A low cost all-digital demodulation method for fiber-optic interferometric sensors

Abstract

Presented in this paper is a novel digital demodulation method for fiber-optic interferometric sensors. The method controls the modulation depth at π/2 radians and uses only five key points sampling values every modulation period. Both an automatic accurate sampling method and a modulation depth control method are introduced. Fewer resources are needed for the calculation processes to obtain the phase shift. High speed A/D converter is not necessary, which results in significant reduction of the manufacturing cost of fiber-optic interferometric sensors. A bias stability of 0.64 deg h −1 (i.e. 2.23 µrad) is demonstrated after using this method on an interferometric fiber-optic gyroscope (IFOG) based on the Sagnac effect.

Digital Control and Demodulation Algorithm for Compact Open-Loop Fiber-Optic Gyroscope

“…In terms of hardware circuits and control algorithms, the current research focuses on the realization of a more stable and concise control algorithm to reduce the computational power requirements of the processor. Therefore, it becomes possible to use a simpler hardware configuration to achieve high-precision control of a gyro, thereby reducing the control circuit footprint and cost [ 10 , 11 , 12 ].…”

“…The conventional open-loop gyroscope algorithm demodulates synchronously the amplitudes of the first, second, and fourth harmonic components of its temporal interference waveform, which requires complex multiple synchronous phase-locked solutions and a powerful convolution processor with a high cost and large footprint [ 13 ]. In order to overcome this problem, some researchers have produced a solution of characteristic points in the modulation period [ 12 ], which can simplify the algorithm. However, this method suffers from a low signal-to-noise ratio.…”